Safety valve



Patented Apr. 2, 1929.

UNITED STATES 1.7074541 PATENT OFFICE.

JOHN PRENTICE; F BAYONNE, NEW JERSEY, ASSIGNOR TO THE BABCOCK & WILCOX COMPANY, OF BAYONNE, NEW JERSEY, A CORPORATION OF NEW JERSEY.v

SAFETY VALVE.

Application filed larch 7, 1928. Serial No. 259,718.

This invention relates to a safety valve for a steam boiler that is provided with a superheater for the steam. In such boilers there is a drop in pressure between the saturated steam in the boiler drum and the superheated steam passing out of the superheater due to the friction in the superheater. It is important that the superheater safety valve shall open before the saturated steam safety valve on the boiler drum which is first to open. It is also important that the range of setting between the super-heater safety valve and the saturated steam safety valve which is the first to open shall not, be too great as this results in a loss due to an undue lowering of the pressure leaving the superheater below that for which the boiler is built. By the present invention the saturated steam pressure is utilized in part for the opening of the superheater safety valve and the arrangement is such that the superheater safety valve will open when the steam in the steam and water drum reaches a predetermined pressure irrespective of what the pressure at the superheater outlet may be through the loss of pressure due to the friction of the steam in flowing through the superheater. By making the predetermined pressure, say

lbs. per sq. in. below that at which the first saturated steam safety Valve will open, the desired result of having the superheater safety valve to be the first to open will be accomplished.

The invention will be understood from the description in connection with the accompanying drawing, in which Fig. 1 is a vertical section on an enlarged scale of an illustrative embodiment of the invention along the line 11 of Fig. 2; Fig. 2 is an outside view of the assembled safety valve partly broken away to show the method by which the valve is mechanically operated by levers and fulcrums to test its condition from time to time, and Fig. 3 shows a cross section along the line 3-3 of Fig. 2.

In the drawings reference character 5 indicates a valve casing which may be attached to a superhcater outlet or any other convenient place where superheated steam at the pressure of the su erheater outlet exists. This valve is provided with the usual valve disc against which the superheated steam presses tending to open the same. The outlet 6 from the casing 5 is for conveyin away the waste steam when the valve m e casdistance from the casing.

portion 13 is provided with a central 'threaded hole into which the guide 11 is screwed. A nut 14 is threaded upon the upper threaded'end of the valve stem 7 and is held in place by means of a cross pin 15.

A housin 18 has a lower flange 19 by which it is bolted to the upper portion of the frame 12. A pivot pin 20 is moltnted on a lug at one side of the lower end of the housing 18 and two parallel spaced levers 21 have one end of each pivoted to the pivot pin 20. The other ends of the levers 21 are provided with a cross pin 22 to which one member 23 of a toggle is pivoted. The member 23 of the toggle is pivoted to the other member 24 of the toggle which is in turn pivoted at 25 to the lower portion of the frame 12. A support 26 projects outwardly from the same side of the frame 12 and a lever 27 is pivoted thereto as shown at 28. The'upper cam portion 29 of the lever 27 bears against the joint of the toggle as shown at 30 to straighten the toggle and lift the left hand end of the lovers 21 for a purpose to be described below.

The upper end of the housing 18 is provided with a flange 31 to which the flange 32, having a boss 33,-is bolted by means of the stud bolts 34. A gland 35 is screwed into an internally threaded hole in the boss 33.

An opening 36 for saturated steam extends into the upper solid portion of the housing 18 and an opening 37 for superheated steam extends into a chamber 37 in the upper portion of the housing 18. Internally threaded rings 38 and 39 are located in'the chamber 37' and discs 40 and 41 threaded on their peripheries are screwed into the rings 38 and 39. The disc 38 is provided with a lower threaded extension 42 and a central opening. 43 extends through the disc and a portion of the extension 42 and communicates with a .cross opening 43' that communicates with a recessed chamber 42 to which the opening 36 leads. A flat threaded nut A and a pyof cross bars 62 extends through the housing d 47. Superheated steam also ramidal jamb nut are provided for the threaded end of theextension 42 and a gasket 46- mayube placed below the disc 40, as indicated, to prevent leakage when the nut 44 is tightened. The jamb nut '45 operates as a stop to limit the upward travel of the valve stem 7 and can be adjusted to different positions for that purpose.

A bellows 47 of a well known type is located in the chamber 37 in the upper portion of the housing 18 and has flanges 48 at the ends of the bellows that are clamped between flanges 49 on the rings 38 and 39 and the discs 40 and 41. The effective external end area of the bellows 47 is preferably made approximately equal tothe area of the valve discat the lower end of the stem 7. An external groove 50 is provided onthe ring 38 and a cylinder 51 may have a rib rolled into this groove. The cylinder 51 extends upwardly to enclose the bellows 47 and ring 39. The disc 41 is provided on its upper side with a central boss 55 and a rod 56 provided with an opening 57 around the boss 55 extends through the boss 33, a recess 58 being left to permit the enlarged. lower end of the rod 56 to move longitudinally.

A cross bar 59 extends across the upper end of the rod 56 and is provided with a recess into which the upper end of the rod extends.

Rods 60 on opposite sides of the housing 18 have their upper endsheld to the ends of the cross bar 59 in adjustable positions by means of the nuts 61. The rods 60 may pass through guide holes in the flanges 31 and 32. A pair 18 and are attached to the lower ends of the rods 60 by means of the-bolts and nuts 63 and 64.

The operation is as follows: superheated steam or steam at the pressure at the superheater outlet enters the chamber 37 through the opening 37, and surrounds the outside of the bellows 47 while steam at the pressure of the saturated steam enters through the openings 36' and 43 into the inside of the bellows entering the valve casing 5 presses against the lower side of the valve disc on the valve stem 7 tending to open the same. When the pressure of the superheated steam in the valve casing 5, supplemented by the differential of pressure on the outside and inside of the bellows 47, is sufficient to overcome the spring 9, the valve is opened and excess steam escapes to lower the pressure. The guide 11 can be screwed in to different distances for the purpose of adjusting the tension of the spr1ng 9 and thereb will open. The differential in pressure on the outside and inside of the bellows 47 operates to aid in o )ening the valve in the casin- 5 because the igher pressure of saturated steam inside the bellows forces the disc 41 against the rod 56 which forces the cross bar 59 upwardly thereby carryingthe cross bars 62 upwardly by means of the rods 60, thus causm pressed and aid in opening the valve.

The lever 27 can be used Whenever desired to open the valve manually in the casing 5 by causing the cam portion 29 to partially straighten the toggle members 23 and 24, thus ralsing the lever 21, cross bars 62, nut 14 and valve stem 7.

The arrangement of the bellows and associated parts in the chamber 37 is such that the same can be removed for repair and replacement due to the fact that the flange 32 and .boss 33 are bolted to the flange 31 at the upper end of the chamber 37.

I claim:

1. In a safety valve for a steam boiler that produces saturated steam .and superheated steam, a spring pressed valve disc havinga stem, means to cause superheated steam to the nut 14 on the valve stem 7 to be press against the face of said valve disc and means for causing differential pressure between the saturated and superheated steam to press against said valve stem.

2. In a safety valve for a steam boiler that produces saturated steam and superheated steam, a spring pressed valve disc having a stem, means to cause superheated steam to press against the face of said valve disc and means for causing difierential pressure between the saturated and superheated steam to press against said valve stem, said differential pressure being obtained from an area approximately equal to the area of said valve isc.

3. In a safety valve for a steam boiler that produces saturated steam and superheated steam, a spring pressed valve disc having a stem, means to cause superheated steam to press against the face of said valve disc,

means for causing differential pressure bc tween the saturated and supperheated steam to press against said valve stem, and meansto limit the extent of travel of said valve disc.

4. In a safety valve to be operated by satrated steam at one pressure and superheated steam at a lower pressure, a spring pressed valve disc, a bellows, means for leading superheated steam to said valve disc and saturated steam to the inside of said bellows to operate said valve.

5. In a safety valve to be operated by saturated steam at one pressure and superheated steam at a lower pressure, a spring pressed valve disc, a bellows, means for leading superheated steam to said valve disc and to the outy side of said bellows and saturated steam to regulating the pressure at which the valvethe inside of said bellows to operate said valve.

6. In a safety valve to be operated by saturated steam at one pressure and superheated steam at a lower pressure, a sprin pressed valve disc, :1 bellows, means for lea mg superheated steam to said valve disc and saturated steam to the inside of said bellows to operate said valve, and a stop to limit the extent of travel of said valve disc.

7. In a safety valve to be operated. by saturated steam at one pressure and superheated steam at a lower pressure, a spring pressed valve disc, a bellows connected to said valve disc, said bellows being surrounded by superheated steam and filled with steam at the pressure of the saturated steam.

8 In a safety valve to be operated by saturated steam at one pressure and superheated steam at a lower pressure, a s ring pressed valve disc, a bellows, means for eading superheated steam to said valve disc and saturated steam to the inside of said bellows, the efiective area of said bellows being approximately equal to the area of said valve disc.

9. In a safety valve to be operated by saturated steam at one pressure and superheated steam at a lower pressure, a spring pressed valve disc, a bellows having a vertically ided movement, means. for leading supereated steam to said valve disc and saturated steam to inside of said vertically guided bellows, the effective external end area of said bellows being approximately equal to the area of said safety valves.

10. In a safety valve to be operated by saturated steam at one pressure and superheated steam at a lower pressure, a spring pressed valve disc, a bellows having a vertically guided movement, means for leading superheated steam to said valve disc and saturated steam to inside of said vertically guided bellows, the effective external end area of said bellows be-' ing approximatel equal to the area of said safety valves, an means provided whereby the upward movement of bellows may be va-- ried and fixed.

11. In a safety valve to be operated by sulurated steam at one pressure and superheated steam at a lower pressure, a spring pressed valve disc, a bellows having a vertically guided movement, means for leading superheated steam to said valve disc and saturated steam to inside of said vertically guided bellows, the efiective external end area of said bellows bein approximately equal to the area of said sa ety valves, the arrangement of the bellows and related parts and'their' housing being such that they may be removed for repairs without interfering with the operation of the superheated safety valve to which it is attached.

JOHN PRENTIGE. 

